Design of a Heating System with Geothermal Energy and CO2 Capture

Design of a Heating System with Geothermal Energy and CO2 Capture

Reyes Lastiri, D.

Wolf, K.H. (mentor)

Applied Sciences

Geotechnology

Sustainable Energy Technology

2013-11-29

Heating constitutes about 40% of the final energy consumption at TU Delft. In the present, the district heating system in campus obtains its energy from the combustion of natural gas in a combined heat and power plant. Although this plant produces heat and electricity with an efficiency over 80%, the dependance on a fossil fuel presents an opportunity for improvement by introducing a renewable energy source. In May 2013, the drilling for a geothermal plant in campus was approved. The present heating system operates at high temperature (HT - 130°C) with 3-way valves. In the new heating system, a geothermal plant will provide part of the energy and some buildings will undergo renovations to work at medium temperature (MT - 70°C); they will be connected in series after HT buildings, constituting a cascade system. In this study, steady state simulations of the heating system are performed using Cycle-Tempo. The results are then used for an exergy analysis of different configurations in the system. The analysis of the ongoing transition in the present heating system from a 3-way to a 2-way valve configuration reveals that up to 180 kW of electricity from the grid used for pumping can be saved and replaced by heat produced locally at a higher efficiency, representing up to 36% in primary energy savings. Within the system boundaries, the exergy efficiency does not improve with the transition, but a reduction in the return temperature from 75-80°C to 50-75°C allows for geothermal energy utilisation. For the new heating system, three configurations of the network are devised: a parallel network at high temperature, a cascade system renovating small buildings and a cascade system renovating large buildings. The exergy analysis reveals that the best option is to renovate the small buildings in campus. In this way, geothermal energy can provide 19% to 50% of the heat demand. The suggested configuration for the new system can operate with an exergy efficiency 14% higher than the present system, reducing the primary energy consumption and the associated emission of CO2 by 47%. Carbon capture and sequestration can decrease the emission of CO2 further by 51%. However, the capture process by means of the dominant technology, amine absorption, requires additional consumption of fossil fuels, which worsens the scarcity of these resources.

district heating
exergy analysis
geothermal energy
carbon capture and storage

http://resolver.tudelft.nl/uuid:bb75bffe-3ceb-4784-b48d-f53f79632a76

Student theses

master thesis

(c) 2013 Reyes Lastiri, D.